The present disclosure relates to the field of spectacles and hinges for spectacle frame. The present invention more particularly relates to an improvement of a hinge for spectacle frame of the type described in the patent application WO 2005/121 873.
The present invention thus relates to an elastic hinge for spectacle frame, comprising an articulation endpiece attached to the frame, linked by a hinge axis to a hinge element attached to a frame temple. The endpiece comprises two parallel flanges sandwiching an articulation knuckle provided at an end of the hinge element. Each of the two flanges and the knuckle has an articulation orifice provided to receive a fixing element like a screw, forming the rotation axis of the hinge.
The hinge element is shown in FIG. 1. In FIG. 1, the hinge element 100 comprises a case 101 comprising a longitudinal housing 103 with a front orifice. The longitudinal housing 103 comprises a guiding area 102 and at least one cavity 104 comprising a retaining wall 105, a slide 110 arranged in the housing according to a longitudinal translation axis, a spring 125 for returning the slide to a rest position, and a bushing 120. The slide 110 comprises a salient part 111 spreading out to the outside of the housing 103 and forming the articulation knuckle, a guided part 112 interacting with the guiding area 102, a central part, and a rod. A compression part 113 attached to the rod, forms a rear stop for the spring 125. The bushing 120 forms a front stop for the spring, and comprises a body 122 slidably mounted around the rod of the slide and at least one elastic tab 121 facing towards the front of the housing 103 according to a determined angle, which end leans against the retaining wall 105. Generally, the bushing comprises two elastic tabs which ends lean on retaining walls opposite from one another provided in the housing.
Consequently, when the slide 110 is pulled forward, the bushing 120 is blocked in translation and the spring 125 is compressed between the compression part 113 attached to the slide and the body 122 of the bushing 120 blocked in the housing 103.
Such a hinge element has a length of a few millimeters only and is usually used in the industry of spectacles.
The hinge previously described ensures a mechanical coupling between the frame and a spectacle temple having the drawback of cumulating clearances in rotation according to axes perpendicular to the axis of the hinge, both between the endpiece and the knuckle of the slide, and between the slide and the case.
The patent application WO 03/071 338 describes a compact elastic hinge for spectacle frame, shown in FIGS. 2 and 3. In FIGS. 2 and 3, the hinge comprises an articulation endpiece 150 attached to a spectacle frame, linked to a hinge element 130 attached to a frame temple. The endpiece 150 comprises two parallel flanges 151a, 151b sandwiching an articulation knuckle 145 formed at an end of the hinge element 130. Each of the two flanges 151a, 151b and the knuckle 145 have an articulation orifice provided to receive a fixing element like a screw, forming the rotation axis of the hinge.
The hinge element 130 comprises a case 131 comprising a longitudinal housing 132 with a front orifice. A slide 140 is arranged in the housing 132 according to a longitudinal translation axis. The slide is returned to a rest position by a return spring 135. The slide 140 comprises a salient part 145 spreading out to the exterior of the housing 132 and forming the articulation knuckle, a central part 143, a rod 142 and a compression part 141 attached to the rod, forming a rear stop for the spring 135. The salient part 145 has the shape of a T with an articulation orifice 146. The case 131 comprises a bump 134 forming the front stop for the spring 135, opposite the central part 143 of the slide. Thus, when the slide 140 is pulled forward outside the housing 132, the spring 135 is compressed between the compression part 141 attached to the slide and the bump 134.
To reduce the length of the slide and therefore of the case 131, the latter comprises an upper prominence 133a and a lower prominence 133b formed in the prolongation of the edge of the front orifice of the housing, these two prominences forming a lateral guiding area of the slide, exterior to the housing. The salient part 145 of the slide comprises a guided part with guiding surfaces 144a, 144b interacting with both prominences 133a, 133b. When the hinge element 130 and the endpiece are assembled, the salient part 145 of the slide 140 and the prominences 133a, 133b are inserted between the flanges 151a, 151b of the endpiece 150. That way, the flanges also perform a lateral guiding of the slide.
In the hinge shown in FIGS. 2 and 3, all the stresses exerted on the hinge according to axes perpendicular to the rotation axis of the hinge are concentrated on the flanges of the endpiece. To ensure an efficient guiding of the slide, the prominences 133a, 133b must have a sufficient length and rigidity. To that end, the dimensions of the prominences must be relatively important. The result is that the flanges must also have relatively important dimensions to free sufficient space in the endpiece around the rotation axis of the hinge, allowing the knuckle and the prominences to freely rotate. Flanges of relatively big dimensions must also be provided to ensure a correct guiding of the slide. This constraint turns out to be penalizing concerning the resistance of the endpiece against rotation stresses exerted on the temple around axes perpendicular to the axis of the hinge. The result is that the flanges tend to move aside in the long run, which causes an important clearance in the hold of the temple on the frame. The slide is then guided with a more important lateral clearance in directions according to the axis of the hinge. Such a clearance has the consequence of applying to the rod 142 of the slide bending stresses that may cause the break thereof.